Capillary electrophoresis is a technique for moving samples of interest through a solution filled capillary by means of an electric field. In such a way, molecules of different mobilities are separated into distinct zones for detection. In the 1990's, significant research effort in the field of capillary electrophoresis was focused on implementation of such capillary electrophoresis devices in microfabricated formats. Such formats provided significant advantages in terms of precision. As a result, micromachining and miniaturization of such devices was established and many applications of such devices subsequently arose in the literature over the next ten years. Such devices are capable of providing fast, efficient separation results for double stranded DNA chromatography, single stranded DNA chromatography, protein analysis and many other applications.
Central to the efficiency of such devices is channel length. For instance, in applications such as DNA sequencing, a longer reading length is important to the throughput and speed of the entire sequencing effort. Devices with separation channels varying from 1 cm up to 10 cm have been demonstrated within the art. However, these microfabrications still suffer some drawbacks. First, microfabrication with long channel length requires large size devices, resulting in expensive fabrication costs. By contrast, low cost microfabrication is dependent on economy of scale, in which hundreds to thousands of devices per wafer are constructed.
To achieve long channel lengths and still maintain a reasonable device area, one has to produce a separation channel that is folded in a serpentine configuration or curved in a spiral configuration. Unfortunately, such curved channels inevitably reduce the efficiency of the overall separation compared with that of a straight separation channel.
Long channel lengths are not the only factor requiring large chip sizes. The drilling process that drills holes through the substrate layers to access the microchannels also increases the device size. Although drilling in glass substrates can be performed to diameter less than 0.5 mm, typically capillary electrophoresis devices employ holes larger than 1 mm for handling purposes.
Given the above background, what is needed in the art are improved capillary devices and methods for making such devices.